Effect of the Application of the Global Lung Initiative 2012 Spirometry Reference Equation on the Diagnosing and Classifying Degree of Airway Obstruction in Thai Adults Aged 40 to 80 Years Old

Abstract

Background and objective: Changing to a different spirometry reference equation can result in misinterpretation of spirometric findings. Currently, there is limited data about any discordance between the interpretations of airway obstruction (AO) using the Global Lungs Initiative (GLI) 2012 and the currently employed Thai reference equations (Siriraj) in Thai adults. Therefore, this study aimed to determine differences in diagnosis around AO and classification of the severity of AO using the GLI2012 and Siriraj reference equations in Thai adults. Materials and Methods: We analyzed spirometric results from Thai adults aged 40–80 years old (n = 2084), which were collected at the Lung Health Center, Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand between January 2005 and December 2015. The diagnoses concerning the AO were interpreted using the GLI2012 and Siriraj reference equations. The severity of AO in each case was classified into five grades, including mild, moderate, moderately severe, severe, or very severe. McNemar’s test was used to analyze differences in diagnosis of AO and classification of the level of severity. The Kappa statistic was used to determine agreements of diagnosis of AO and classification of severity between the two reference equations. Results: There were significant differences in both diagnosis of AO and their classifying severity level between the two reference equations (p-value < 0.001). However, the levels of agreement between the two reference equations were moderate to very good in different age and sex groups (Kappa values ranged from 0.62 to 0.78 for the diagnosis of AO and 0.54 to 0.89 for the classification of severity). Conclusions: Changing from the Siriraj to the GLI2012 reference equations underestimates the proportion of airway obstruction in Thai adults.

Defining and Grading an Obstructive Ventilatory Impairment: American Thoracic Society/ European Respiratory Society Interpretive Strategies of 2005 Versus 2022

“…For the cases with normal FEV1 z-score, they were considered mild using FEV1%. These findings were on line with previous studies conducted by LINARES-PERDEMO et al, VUKOJA et al, and CHAIWONG et al, who have compared different reference equations used to define the LLN of FEV1 and FEV1/FVC ratio to define an OVI and grade its severity [17][18][19] and concluded that significant differences existed when classifying degree of lung function impairment with different predictive equations in patients with obstructive lung diseases [20]. The meaning of a low FEV1/FVC ratio with a normal FEV1 is unclear.…”